1. Field of Invention
The invention relates to a liquid ink cartridge for a liquid ink image forming apparatus. The liquid ink cartridge uses a viscous gel seal that maintains the ink supply below atmospheric pressure to avoid undesired seeping of the ink from ink nozzles, particularly when the apparatus is idle. Thus, the present invention avoids the drying and clogging of the nozzles over extended periods of disuse.
2. Description of Related Art
A common design feature for all ink jet cartridges is a method to maintain a negative supply pressure. This negative pressure is needed so that ink will not be released out of the cartridge opening in a rest state. Generally, this negative pressure can be supplied by using any one of three different methods: 1) use of a foam capillary media to hold ink back, 2) use of a spring inside a bag to create a vacuum, and 3) placement of the ink container physically below the printing element.
The disadvantages of these methods include: 1) foam containers use an additional part that requires a difficult assembly operation. Foam containers may also deprime over time as the foam has a tendency to draw in a mix of air and ink; air trapped in the foam interrupts the flow of ink through the foam. As a result, foam containers generally have low ink delivery efficiency due to the amount of ink left in the foam at the end of the container's life. 2) A spring bag is expensive and will have a change in delivery pressure over the life of the container due to the spring rate of the material. 3) Placement of the ink container below the printing element is difficult to implement in many space constrained architectures and typically requires an umbilical system with connect and disconnect seals.
In ballpoint pens, the use of ink follower compositions, also known as “grease plugs,” have been employed to prevent backleakage of the ink, inhibit evaporation of solvents and to reduce the risk of forming air gaps in the ink tube. Typically, ink followers are composed of a non-polar liquid, which is thickened to a grease-like consistency via the use of a thickener, and are positioned behind the ink supply. Such compositions also maintain negative pressure.
U.S. Pat. Nos. 3,526,522 and 3,656,857, to Seregely, disclose ink follower compositions containing a liquid vehicle and solid, microscopic grains or particles of organic plastic or polymer. U.S. Pat. No. 5,348,989, to Shiraishi, discloses ink volatilization-preventing compositions that contain a slightly volatile organic liquid, a gelling agent and a polyether-modified silicone.
These ink control plugs can sufficiently prevent the ink from leaking out when the aqueous ballpoint pens are positioned in a vertical or horizontal orientation, and they withstand a light drop impact. Of the light drop impacts, the strongest example is a case where the pen drops on a floor from a desk (about 70 cm). In this case, even a conventional ink follower scarcely gives rise to any trouble, through the ink follower slightly shifts.